This section provides background information related to the present disclosure which is not necessarily prior art.
Technical Field
The invention relates to an arrangement for double-sided printing of thermal paper, comprising a first print head for printing the front side of the thermal paper and a second print head for printing the back side of the thermal paper.
Discussion
Printers of this type are in particular used as receipt printers, for example, for printing receipts in reverse vending machines or for printing cash register receipts in the retail trade. Further, receipt printers are used in various machines such as ticket machines, and systems for printing vouchers, tickets and receipts.
Thermal printers for double-sided printing of thermal paper are, for example, known from documents U.S. Pat. No. 7,710,442 B2, EP 1 321 296 A2 and U.S. Pat. No. 6,784,906 B2. In the known printers, the thermal paper is guided between a print head and a counter-pressure element so that the thermal paper rests against the respective print head for printing. In a maintenance mode, in particular for removing a paper jam or for inserting thermal paper unrolled from a roll into the printer, the print heads and the counter-pressure elements are separated from one another. In specific arrangements, a first print head and a first counter-pressure element are arranged in a lower first unit and a second print head and a second counter-pressure element are arranged in an upper second unit. The second unit is connected to the first unit in the form of a hinged cover so that when the cover is hinged open, the print heads and the counter-pressure elements are separated from one another so that the thermal paper can easily be inserted and/or can easily be removed in the area of the print heads.
The first print head and the second counter-pressure element are arranged opposite to each other and form a first printing mechanism. The second print head and the first counter-pressure element form a second printing mechanism. As a result thereof, the print heads and counter-pressure elements belonging to one printing mechanism are held in different units so that the printing quality of the print image generated with the aid of these printing mechanisms is highly dependent on the exact positioning of the two units to each other.